I used the keywords "internet marketing" in MERLOT and found 63 results which include textbooks as well as assignments and textbook companions. I'm not sure if the url to my search is a "persistent" link, but here it is: https://www.merlot.org/merlot/materials.htm?keywords=internet+marketing&sort.property=relevance&btn_0=Search
While the search "internet marketing" yielded 0 results, I browsed their category of "marketing" and there are more than a dozen marketing textbooks.
